Bar codes (price, inventory and so on) are printed on some consumer item packaging. At the check-out counter the code is scanned photoelectrically or by laser, or otherwise. The resultant image is transformed to appropriate register analog data including the sales price.
In some kinds of packages, particularly cardboard, the code when printed by ink is frequently blurred. The ink "bleeds," expanding the code bars, because too much ink may have been applied. The code is therefore indistinct and the transformed data are garbled, so to speak.
Thus, there is a demand that scanning of bar codes particularly on corrugated package material, be achieved with assurance of accuracy.
To print bar codes that are consistently scannable is by far the most difficult printing requirement that any corrugated manufacturer has to contend with; the failure rate is extremely high. Cross section samplings continue to show a failure rate of 25% to 40%. These failures are caused in part because of the inability to control the ink application when using rubber or photopolymer plates. Improper bar code specifications and variables for corrugated applications also enter the picture.
For a bar code to be scannable, the various vertical lines (bars) must be an exact dimension plus or minus a few thousandths depending on the nature and size of the code. This is difficult for the corrugated printer to achieve because of the following:
1. Irregularity of corrugated board. PA1 2. Expansion of rubber or photopolymer printing plates. PA1 3. No press controls for maintaining optimum inking of the printing plates.